1. Field of the Invention
The present invention relates to a halogen-free flameproof mesh sheet used outdoors such as at a construction site, and in particular to flameproof mesh sheets capable of being used for a long time.
2. Description of Related Art
In recent years, there has been a trend toward the construction of buildings having a large number of stories in the construction industry. Meanwhile, there has also been an increase in the number of houses having a relatively small number of stories. There has recently been an increase in the need for flameproof mesh sheets, for example for safety and protection in houses having a small number of stories and also for scattering prevention. Due to these and other factors, flameproof mesh sheets must be laid in these buildings. Further, regulations are becoming more and more strict regarding their use.
Currently used flameproof mesh sheets and scattering prevention flameproof mesh sheets are generally produced by weaving yarn prepared by coating a polyester, nylon or polypropylene multi-filament fiber with a vinyl chloride-based paste resin composition and heating, and then heating the obtained cloth. In addition, they can be prepared by coating a fabric prepared by weaving and processing a multi-filament fiber with a vinyl chloride-based paste resin composition, heating and processing to a desired shape.
An exemplary resin composition for coating a fiber and fabric comprises a vinyl chloride resin containing chlorine as a resin and a chlorine-based flame retardant such as chlorinated paraffin, bromine-based flame retardant such as decabromodiphenyl oxide or an inorganic flame retardant such as antimony trioxide (see, for example, Examined Japanese Patent Publication Nos. 52-41786, 53-18065 and 61-94305, Plastics, February, 1991 which is incorporated herein in its entirety by reference).
In recent years, it has been demanded globally to avoid the use of resins and flame retardants containing elemental halogen which generate harmful gas at the time of combustion from the viewpoint of the environmental preservation of the earth.
Japanese Laid-open Patent Application No. 61-223045 proposes that red phosphorus and ammonium phosphate can be kneaded into a polyolefin to prevent corrosion by elemental halogen contained in an elemental halogen-containing compound flame retardant. However, a flame retardant prepared by dispersing red phosphorus and ammonium phosphate in an aqueous dispersion of an ethylene-vinyl acetate copolymer or an aqueous dispersion comprising the aqueous dispersion and an aqueous dispersion of an .alpha.-olefin copolymer and/or an aqueous dispersion of a polyurethane was not known at the time of the present invention.
The inventor of the present invention has proposed in Japanese Laid-open Patent Application No. 9-225464 which is incorporated herein by reference in its entirety a halogen-free flame retardant comprising an aqueous dispersion of a polyolefin resin as a flame retardant. This flame retardant has an excellent effect but it has a tendency to increase in viscosity over time during storage.